From 3e258c5d9d3ed66bd52303ec5f18933f1b76769a Mon Sep 17 00:00:00 2001
From: Eric Vergnaud <eric.vergnaud@wanadoo.fr>
Date: Sat, 24 Aug 2019 01:46:11 +0800
Subject: [PATCH] avoid hashCode == 0

---
 runtime/JavaScript/src/antlr4/PredictionContext.js | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/runtime/JavaScript/src/antlr4/PredictionContext.js b/runtime/JavaScript/src/antlr4/PredictionContext.js
index e69cdea37..8b2e2ece0 100644
--- a/runtime/JavaScript/src/antlr4/PredictionContext.js
+++ b/runtime/JavaScript/src/antlr4/PredictionContext.js
@@ -111,11 +111,13 @@ Object.defineProperty(PredictionContextCache.prototype, "length", {
 
 function SingletonPredictionContext(parent, returnState) {
 	var hashCode = 0;
+	var hash = new Hash();
 	if(parent !== null) {
-		var hash = new Hash();
 		hash.update(parent, returnState);
-        hashCode = hash.finish();
+	} else {
+		hash.update(1);
 	}
+	hashCode = hash.finish();
 	PredictionContext.call(this, hashCode);
 	this.parentCtx = parent;
 	this.returnState = returnState;